1. Field of the Invention
This invention relates to an ink supply device in an ink jet recording apparatus, and in particular to an ink supply device of the type in which ink is supplied to a recording head from a hermetically sealed ink bag formed of a flexible material such as a plastic sheet.
2. Related Background Art
As one type of a recording apparatus such as a printer or an image forming apparatus, use is made of an ink jet recording apparatus in which ink droplets are caused to fly from a plurality of ink discharge ports to thereby form dot patterns on a sheet (a recording medium such as recording paper or a plastic sheet).
Ink which is a recording agent is usually supplied from an interchangeable ink container set at a predetermined location in the recording apparatus to a recording head (ink jet head) through an ink supply tube.
Where a hard box type container is used as the ink container, a vent hole for eliminating any variation in internal pressure is necessary, and this leads to problems; for example, ink, solvent evaporates to degenerate (increase the viscosity of) the ink or cause leakage of the ink.
So, it has been practised to use as the ink container a hermetically sealed ink bag formed of a flexible material such as a plastic sheet.
In this case, a plug member is attached to the ink bag in a sealing manner so that ink in the ink bag may be supplied to the recording head through an ink supply path formed, for example, by a hollow needle or the like through the plug member.
Also, this ink bag is used while being usually contained at a predetermined position within the case of a cartridge.
Now, the ink supply device according to the prior art has suffered from the following problems.
Firstly, the air in the ink bag goes round to the neighborhood of the inlet of the ink supply path formed by the hollow needle or the like, and this has sometimes caused unstable feeding of the ink or clogging of the ink supply path.
Also, the plug member has been insufficient in its close contact with the ink bag and thus, the sealing property of the sealed portion has been liable to become insufficient.
Further, in some cases, when containing and holding the flexible ink bag within the case of a cartridge, it has been difficult to position the ink bag and maintain its shape.